1. Field of the Invention
The present invention relates to a thin film magnetic film head structure for manufacturing a thin film magnetic head having at least an inductive magnetic transducer for recording, a method of manufacturing the same, and a method of manufacturing a thin film magnetic head by using a thin film magnetic head structure.
2. Description of the Related Art
In recent years, as the areal density of a magnetic recording medium (hereinbelow, simply called “recording medium”) such as a hard disk improves, improvement in performance of a thin film magnetic head which is mounted on a magnetic recording apparatus such as a hard disk drive (HDD) is demanded. Known recording methods of a thin film magnetic head are a longitudinal recording method in which the orientation of a signal magnetic field is set to an in-plane direction (longitudinal direction) of a recording medium and a perpendicular recording method in which the orientation of a signal magnetic field is set to a direction orthogonal to the surface of a recording medium. At present, the longitudinal recording method is widely used. However, when a market trend accompanying improvement in areal density of a recording medium is considered, it is assumed that, in place of the longitudinal recording method, the perpendicular recording method will be regarded as a promising method in future for the following reason. The perpendicular recording method has advantages such that high linear recording density can be assured and a recorded recording medium is not easily influenced by thermal decay.
A thin film magnetic head of the perpendicular recording method has a thin film coil for generating a magnetic flux and a magnetic pole layer extending rearward from an air bearing surface and emitting the magnetic flux generated by the thin film coil toward a recording medium. The magnetic pole layer includes, for example, a track width specifying part having a width (uniform width) specifying the recording track width of a recording medium. The height of the track width specifying part in the magnetic pole layer, that is, the distance from the front end (the edge exposed in the air bearing surface) of the track width specifying part to the rear end (the edge on the side far from the air bearing surface) is a neck height as an important factor contributing to recording performances of the thin film magnetic head. In the thin film magnetic head of the perpendicular recording method, when current is passed to a thin film coil and a magnetic flux for recording is generated, the magnetic flux is emitted from the tip of the track width specifying part of the magnetic pole layer, thereby generating a magnetic field for recording (perpendicular magnetic field), and the surface of the recording medium is magnetized on the basis of the perpendicular magnetic field. In such a manner, information is magnetically recorded on the recording medium.
As the thin film magnetic head, recently, a composite-type thin film magnetic head having not only the function of performing a recording process on a recording medium (magnetically recording information on a recording medium) but also the function of performing a reproducing process on the recording medium (magnetically reading the information recorded on the recording medium) (hereinbelow, simply called “composite thin film magnetic head”) is spread. The composite thin film magnetic head has, for example, both of a recording head portion of executing a recording process of the perpendicular recording method and a reproducing head portion of executing a reproducing process by using the MR (Magneto-Resistive) effect. The reproducing head portion includes an MR device extending rearward from the air bearing surface as a main body of executing the reproducing process. The height of the MR device, specifically, the distance from the front end (the edge exposed in the air bearing surface) to the rear end (the edge on the side far from the air bearing surface) of the MR device is an MR height as an important factor contributing to reproduction performances of the thin film magnetic head.
To manufacture a plurality of composite thin film magnetic heads in a lump, composite thin film magnetic heads are manufactured by using a thin film magnetic head structure having a configuration that a plurality of thin film magnetic head precursor are provided on a wafer. The thin film magnetic head precursors are preparatory members to become thin film magnetic heads and are arranged in plural rows on a wafer. In particular, the thin film magnetic head precursor has a configuration similar to that of a completed composite thin film magnetic head including both of a reproducing head portion and a recording head portion, except that the air bearing surface is not formed.
In a process of manufacturing the composite thin film magnetic head, the thin film magnetic head structure is cut in rows of the thin film magnetic head precursors, thereby obtaining a plurality of thin film magnetic head bars. After that, one end face (a cut face of the thin film magnetic head structure) of the thin film magnetic head bar is polished so that the dimension of each of the polished reproducing head portion and the polished recording head portion becomes a predetermined dimension, concretely, the MR height of the reproducing head portion becomes a predetermined dimension and the neck height of the recording head portion becomes a predetermined dimension thereby forming an air bearing surface. It completes the thin film magnetic head. After that, the thin film magnetic head bar in which the air bearing surfaces are formed is cut in thin film magnetic heads, thereby obtaining a plurality of magnetic head sliders.
Some techniques have been already proposed with respect to the process of manufacturing a composite thin film magnetic head in order to control the progress of a polishing process in a polishing step for forming the air bearing surface. Concretely, for example, there is a known technique of forming a dummy sensor for monitoring in a thin film magnetic head precursor in a step of forming the thin film magnetic head preparatory sensor, and executing a polishing process while measuring the MR height by using the dummy sensor (refer to, for example, Japanese Unexamined Patent Application No. H11-000863). There is also a known technique of measuring electrical resistances of a plurality of MR devices in a plurality of thin film magnetic head precursors in place of measuring the MR height and executing the polishing process while calculating an average value of the electrical resistances (refer to, for example, Japanese Unexamined Patent Application No. H02-095572). In the techniques, the polishing amount can be controlled so that the MR height becomes a predetermined dimension.
To assure operation performance of the composite thin film magnetic head, it is necessary to determine, for example, both of the neck height contributing to the recording performance and the MR height contributing to the reproducing performance with high precision. In a conventional composite thin film magnetic head manufacturing method, however, at the time of polishing a thin film magnetic head bar, the progress of a polishing process is controlled so that MR height is determined to become a predetermined dimension among the plurality of thin film magnetic head precursors, but the progress of the polishing process is not controlled so that the neck height is determined to become a predetermined dimension among the plurality of thin film magnetic head precursors. Consequently, from the viewpoint of determining both of the MR height and the neck height with high precision, there is still room for improvement. Therefore, to assure the operation characteristics of the composite thin film magnetic head, it is desired to establish a technique of manufacturing a composite thin film magnetic head in which both of the MR height and the neck height can be determined with high precision in the polishing process for forming an air bearing surface. In this case, particularly, to establish the technique of manufacturing the composite thin film magnetic head, it is also important to establish a thin film magnetic head structure used for the manufacturing technique and a method of manufacturing the same.